In recent years, there have been significant increases of inputting devices which employ so-called touch-panel systems, namely, touch-type inputting devices. In cellular phones, portable gaming machines, and portable music players, as well as in bank's ATMs and ticket-vending machines in stations, there have been largely increased apparatuses which employ touch panel systems as inputting interfaces, along with developments of techniques for thin displays.
As touch panels having been currently used, there have been mainstreams of resistive types and capacitive types and, furthermore, there have been also touch panels of optical types and electromagnetic-induction types, and touch panels which utilize surface acoustic waves through piezoelectricity. In general, information about positions is detected using such schemes. In other words, information about which position on the touch panel has been touched (pressing-manipulated) by an operator is acquired as coordinate information, and specified processing is executed based on this information. As represented by bank's ATMs, by touching the portions of buttons being displayed on the screen, the operator can manipulate the apparatus, as if the operator has performed pressing manipulations on actual buttons. As a result of recent developments of graphic user interfaces (GUIs) processing techniques, there have been also apparatuses which enable operators to scroll images being displayed therein by stroking the screens, and, further, enable the operators to directly control slidable switches being displayed therein as graphics, with their fingers.
There have been a need for a wide variety of touch panels and, recently, there have been an increased need for acquiring information about pressing forces along with information about positions at the same time. That is, if it is possible to detect two types of information about which position on the screen has been touched by an operator and about how strongly the operator has touched it, it is possible to further improve the manipulability.
As a technique relating thereto, JP 5-61592 A (Patent Document 1) discloses a technique for detecting w information about positions and information about pressing forces, by overlaying a position-detecting device and a pressure-sensitive sensor on each other.
Further, JP 2006-163618 A (Patent Document 2) discloses a method for acquiring pressing-force information using a piezoelectric sheet, and for detecting which portions of a plurality of electrode lines formed in a lattice shape on the piezoelectric sheet detection voltages have appeared at, in order to acquire position information.
However, in the touch panel described in Patent Document 1, the pressure-sensitive sensor formed from a piezoelectric sheet or a pressure-sensitive resistance sheet is overlaid on the ordinary touch panel for only positional detection. This pressure-sensitive sensor is overlaid on the entire surface of the touch panel.
In general, such an ordinary touch panel is installed on an image display device of some type, and thus, is required to have higher transparency. Such a position-detecting touch panel and such a pressure-sensitive sensor both include a plurality of films and electrode layers. By making these films transparent, and by employing transparent electrically-conductive materials such as indium tin oxide (ITO) as the electrode layers, it is possible to cause their entirety to have transparency. However, there has been the problem of poor light transmittance, due to many laminated layers. Further, there is a need for larger numbers of components and processes, which involves an increased cost. Further, position information and pressing-force information are detected separately, which has induced the problem of complicacy of signal processing.
On the other hand, the touch panel 2 described in Patent Document 2 is provided with the lattice-shaped fine wiring electrodes on the piezoelectric sheet, in order to detect position information and pressing-force information at the same time. Such position information is acquired based on which electrodes, out of the lattice-shaped electrodes, intensive signals have been detected from. This necessitates connecting all of these fine wires to an operational processing portion, thereby inducing the problem of significant complicacy of the structure.    Patent Document 1: JP 5-61592 A    Patent Document 2: JP 2006-163618 A